[dart_mcp_server] Tighten input and path validation in package tools (#740)

## Summary

Tightens argument and path validation for the package dependency tools (`rip_grep_packages` and `read_package_uris`):

- Ensure `rip_grep_packages` arguments include at least one `-e`/`--regexp` pattern flag, disallow inline values on boolean flags, and make `_runRipGrep` private.
- Pass `--no-config` and `--no-follow` to `rg` for consistent behavior across user environments, and set `additionalProperties: false` on the `rip_grep_packages` input schema.
- Normalize and resolve paths when checking package root bounds in `rip_grep_packages` and `read_package_uris`.
- Use `-NoProfile`, `-NonInteractive`, and single-quoted `-LiteralPath` arguments when extracting ripgrep archives via PowerShell on Windows.
- Bump version to `1.2.3-wip` and update `CHANGELOG.md`.

## Tests

- Added unit tests in `test/tools/grep_test.dart` and `test/tools/package_uri_reader_test.dart` covering pattern flag validation, inline boolean flag values, NUL character rejection, and symlink path handling.